The present invention relates to a method of controlling a threshing mechanism of a combine harvester.
More particularly, it relates to such a method of controlling, in accordance with which the predetermined parameters of the threshing mechanism are adjusted with regard to a nominal crop performance determined for predetermined harvesting conditions, to an optimal value.
Moreover, the present invention also relates to a combine harvester provided with a control arrangement for performing such a method.
Combine harvesters are provided with various working aggregates for treatment of the harvested product stream. Important working aggregates include for example a threshing mechanism for threshing a product stream from which grains have to be removed, a separating device which is located after the threshing mechanism and formed for example as a shaker or a rotor for separating the grains contained in the threshed product stream from further components of the threshed product stream, and the cleaning device composed as a rule of several sieves and a fan for separating the grains from admixtures, such as chaff and short straw. Different parameters of this working aggregates, for example the threshing concave distance and the threshing drum rotary speed of the threshing mechanism or the fan power and the sieve widths of the cleaning device must be adjusted in dependence on the corresponding crop and other harvest conditions, in order to perform a planned harvesting work in an optimal manner.
In connection with this, different objectives can be set in these cases. One of these objectives is to obtain a smallest possible loss rate. A further objective is that, due to the high time pressure, to obtain within the short harvesting period a high throughput or a high surface performance, or in other words to provide harvesting in the shortest possible time. Unfortunately these objectives are not independent from one another, but instead with increasing crop throughput, generally the losses increase as well. The common objective is therefore to obtain a compromise between a still acceptable loss rate and a fast carrying out of the harvesting work.
Due to different properties of the different crop or fruit types, as well as different harvesting conditions such as ripening condition of the crop, grain moisture, straw content, straw moisture, grain size, components density, etc. it is often not simple for a driving operator to adjust all parameters of the working units of the combine harvester. In modern combine harvesters with comfortable control devices, the adjusting values are supplied from a storage device or from a table, which were identified before from test results of the manufacturer of the combine harvester or the operator of the combine harvester.
A method, in which the adjustment parameters for the working units of the combine harvester with inputting a crop type and further crop-specific values as well as the objectives for the planned harvesting work can be obtained from a storage device, is disclosed for example in the German patent document DE 198 00 238 C1. The working units of the combine harvester are adjusted to such optimal values, with which a justifiable loss value can be obtained with the introduced harvesting conditions, in other words the crop properties and other conditions such as ground property, moisture, etc. By means of these adjustments the desired objective is obtained when the combine harvester operates in the most efficient way with a justifiable harvest loss. The driver has only the task to select the harvesting speed, or in other words the traveling speed of the combine harvester, so that actually the predetermined nominal crop throughput is maintained, with respect to which the parameters of the working units are adjusted to the optimal value.
Unfortunately, however the targeted optimal nominal crop throughput can not be always maintained, since suddenly occurring restricting harvesting conditions do not allow the required harvesting speed. Such restricting outer harvesting conditions include for example a so-called down grain, product flow problems in the cutting mechanism, rocky regions in the ground, strong ground unevenness or an overloading of the crop during the travel. Also, with a too careful driver, it can be prevented that the targeted crop throughput is reached. The restrictive harvesting conditions based on the crop itself, or in other words the restricted crop properties include for example a very high straw and/or grain moisture or weeds in the crop stock. The driver is then forced to reduce the harvesting speed. Also, outer harvesting additions can lead to the situation that the driver must suddenly increase the harvesting speed, for example when there is a risk that the weather changes and a predetermined field part must be definitely harvested before it. All these cases lead to the situation that the concrete actual crop throughput deviates from the nominal crop throughput, with respect to the optimal adjustment of the machine parameters.
Each significant deviation of the crop throughput from nominal crop throughput is however disadvantageous, depending on whether it deals with too low or too high crop throughput. When mainly the actual crop throughput is lower than the nominal crop throughput this can lead to the situation that the threshing device of the combine harvester thrashes very small crop quantity too strongly. As a result, many grains are broken in the threshing device (so-called “grain breakage”). The damaged grains can not be used anymore, so that the loss rate is increased. Furthermore, with the too hard threshing, the straw is unnecessarily comminuted in the threshing device and moves then through the threshing concave or through the subsequent separating device into the cleaning device. This leads to an increased cleaning load and a reduced cleaning efficiency. Moreover, it is connected with very high energy use. The different crop properties can further lead to overloading of individual working units, for example the separation rotors, a straw chopper or the drive motor. Very high crop throughput to the contrary leads to the situation that the crop is no longer correctly threshed in the threshing device. The not threshed grains can not be then separated in the subsequent separating device from straw, so that an increased number of grains remains in the straw and thereby the loss rate also increases.
In order to avoid this, in the known method in the case of occurrence of such restrictive harvesting conditions, a completely new optimization of the required adjustment parameters of the working units of the combine harvester is performed. It should be considered mentioned that the majority of restricting harvesting conditions such as for example a down grain, product flow problems, ground unevenness, a crop overloading during the travel or also an increased weed content in the crop, often occur only temporarily or locally within the surface to be harvested. New adjustments of the different parameters are therefore proposed continuously to the driver of the combine harvester during a harvesting work, that additionally burdens the driver and additionally distracts him from the important task to adjust the traveling speed to the outer conditions and to reach the optimal harvesting speed as fast as possible.